The present invention relates generally to optical switching, and, more particularly, to improved optical switching speed, and/or electrical power dissipation, relying on reversible (electrochemical) oxidation-reduction reactions.
Currently, there are a wide variety of known chromogenic materials that can provide optical switching in thin film form. These materials and their applications have been reviewed recently by C. B. Greenberg in Thin Solid Films, Vol. 251, pp. 81-93 (1994); R. J. Mortimer in Chemical Society Reviews, Vol. 26, pp. 147-156 (1997); and S. A. Agnihotry in Bulletin of Electrochemistry. Vol. 12, pp. 707-712 (1996).
Such chromogenic materials are currently being studied for several applications, including active darkening of sunglasses, active darkening of windows for intelligent light and thermal management of buildings, and various types of optical displays (such as heads-up displays on the inside of windshields of automobiles or airplanes and eyeglass displays). Despite their long history of great promise, there are very few photon gating devices made from the existing classes of electrochromic materials. This is because most of them require an oxidation-reduction reaction that involves the transport of ions, such as H+, Li+ or Na+, through some type of liquid or solid electrolyte. Finding the appropriate electrolyte is a major problem, as is the slow speed of any device that requires transport of ions. Furthermore, such reactions are extremely sensitive to background contamination, such as oxygen and other species, and thus degradation of the chromogenic electrodes is a major limitation.
In fact, for photonic switching applications such as a crossbar switch router for a fiber optic communications network, the lack of a suitable chromogenic material has forced companies to use very different approaches: (a) transform the optical signal into an electronic signal, perform the switching operation, and then transform back to an optical signal before launching into a fiberxe2x80x94this is the most frequent solution used today but it is very inefficient and the electronics have a hard time keeping up with the data rates of the optical system; (b) use a moving-mirror array made by micro-electromechanical processing to switch optical data packetsxe2x80x94this has the disadvantage that extremely high tolerances are required for the device, which makes it very expensive, and (c) use ink jet technology to push bubbles into a chamber to create a mirror to deflect an optical beamxe2x80x94this approach again requires precision manufacturing and the switching time is slow.
Thus, there remains a need for an optical switch that can rapidly switch optical signals from one path to another with low power dissipation.
In accordance with the teachings of the embodiments herein, an electrochemically-activated optical switch is provided, comprising a molecular system configured between a pair of electrodes. The molecular system includes a moiety that is oxidizable or reducible in the presence of an electric current induced by an applied voltage of the appropriate magnitude and sign.
A primary advantage of the present invention is simplification (and thus easier manufacturability and lower cost) of the apparatus required for switching.
A second major advantage of the present invention is improved speed of the switching process, since die time scale for switching is determined by the injection or extraction of electrons and holes directly into or from the reductant and oxidant, in a fashion similar to charging or discharging a capacitor, rather than transport of an ion through a thick electrolyte layer.
A third major advantage is that the voltage and the amount of power used to change the color of the structure are quite low, and in fact since the structure is essentially a very thin battery, much of the energy required to store information in the system can be reclaimed later upon erasing or changing the color state of the material.